User Guide

RH180 Manual 25
Size the gas pipe
The gas supply must be capable of handling the enre gas
load at the locaon. Gas line sizing is based on gas type,
the pressure drop in the system, the gas pressure sup-
plied, and gas line type. For gas pipe sizing in the United
States, refer to the Naonal Fuel Gas Code, NFPA 54. The
below informaon is provided as an example. The appro-
priate table from the applicable code must be used.
1. For some tables, you will need to determine the cubic
feet per hour of gas required by dividing the gas input
by the heang value of the gas (available from the
local gas company). The gas input needs to include all
gas products at the locaon and the maximum BTU
usage at full load when all gas products are in use.
2. Use the table for your gas type and pipe type to nd
the pipe size required. The pipe size must be able to
provide the required cubic feet per hour of gas or the
required BTU/hour.
Example:
The heang value of natural gas for your locaon is 1000
BTU/FT
3
. The gas input of the RH180 is 91,500 BTU/HR.
Addional appliances at the locaon require 65,000 BTU/
hr. Therefore the cubic feet per hour = (91,500 +
65,000) / 1000 = 156.5 FT
3
/HR. If the pipe length is 10
feet then the 3/4 inch pipe size is capable of supplying
156.5 FT
3
/HR of natural gas.
Gas Input of all gas products (BTU / HR)
Heang Value of Gas (BTU / FT
3
)
Cubic Feet
per Hour =
Length
Pipe Size (inches)
1/2 3/4 1 1 1/4
10 131 273 514 1060
20 90 188 353 726
30 — 151 284 583
40 — 129 243 499
50 — 114 215 442
60 — 104 195 400
70 — 95 179 368
80 — 89 167 343
90 — 83 157 322
100 — 79 148 304
Pipe Sizing Table - Natural Gas
Inlet Pressure: less than 2 psi (55 inches W.C.)
Pressure Drop: 0.3 inches W.C.
Specic Gravity: 0.60
Schedule 40 Metallic Pipe
Capacity in Thousands of BTU per Hour
Length
Pipe Size (inches)
1/2 3/4 1 1 1/4
10 291 608 1150 2350
20 200 418 787 1620
30 160 336 632 1300
40 137 287 541 1110
50 122 255 480 985
60 110 231 434 892
80 101 212 400 821
100 94 197 372 763
Pipe Sizing Table - Propane Gas
Inlet Pressure: 11.0 inches W.C.
Pressure Drop: 0.5 inches W.C.
Specic Gravity: 1.50
Schedule 40 Metallic Pipe
Capacity in Thousands of BTU per Hour